196 W. B. CHAPMAN 



V. A SHORT DESCRIPTION OF THE EMBRYOS 



Although this problem deals only with the development of the 

 vascular system, I \\t.11 take the liberty to include a brief descrip- 

 tion of the embryo. Many of the embryos developed very abnor- 

 mally, and in some it was impossible to distinguish the anterior 

 from the posterior ends by the shape of the embryo alone, but in 

 chicks where the heart was removed with a minimum of injury 

 to the remainder of the chick, the embryo continued to develop 

 for a time in an almost normal manner. The chick turned 

 upon its left side, the amnion behaved as usual, the eyes were 

 formed, and the wing buds appeared. The most abnormal 

 feature was its failure to grow large. In no case did the embryo 

 exceed 7 mm. in length after the removal of the heart. In a 

 number wherein the heart was injured but not totally destroyed, 

 especiall}^ in the operations with the electric needle, the size of 

 the embrj^o was in proportion to the impairment of the circulation. 



An examination of the embryos without hearts, in serial sec- 

 tions, showed very little that could be interpreted as normal. 

 The neural tube and notochord were present, and the general 

 outer contour had a normal appearance, but the embryo con- 

 tained huge spaces beneath and to the side of the neural tube 

 and notochord and connecting freely with the celomic cavity at 

 many points. These relatively huge spaces are so packed with 

 blood cells that it was often necessary to use the high power in 

 order to tell the wall of the cavity from its contents. Alitoses 

 were numerous both within the substance of the embryo and 

 among the cells inside the open spaces. That several of these 

 spaces were the remains of blood vessels was indicated, but they 

 were very abnormal. 



VI. .MENTION OF RESULTS OBTAINED IN A NUMBER OF OPERATIONS 

 WHICH WERE ONLY PARTIALLY SUCCESSFUL 



The results obtained in a number of operations that were only 

 partially successful are worth mentioning. In an effort to pre- 

 vent the formation of the heart, I tried cutting through the lat- 

 eral plates and dissecting around the neural tube of a number of 



